Twisted stem tools have been made and used for many years. In twisted stem tools, the bristles or brush material is secured in the bight of a wire or cotter pin with the legs twisted about a common axis. The brush material is then usually disposed in a helix and the projecting twisted stem becomes the drive arbor for powered tools. Such tools find wide application in small size or low torque applications. Examples of such applications would be anything from eyelash applicators to bottle brushes. In fact, the type of tool is often times known as a bottle or tube brush regardless of application.
Bottle or tube brushes are sometimes made with two to four pieces of wire which are held at both ends and then twisted about a common axis resulting in a helical tube or bottle brush. This method then requires a stem on both ends of the brush and one may be used for driving the brush.
Twisted stem tools and their methods of manufacture are shown in the following U.S. patents to Osborn Manufacturing of Cleveland, Ohio:
U.S. Pat. Nos. 2,465,396 PA1 2,580,378 PA1 2,603,921 PA1 2,690,631 PA1 2,895,155 PA1 2,972,157
The advent of abrasive loaded plastic monofilaments and tapes used for abrading and honing tools has created problems in the manufacture of such twisted stem abrading and honing tools. Such monofilaments or tapes are usually made of nylon with a suitable abrasive mixed therein homogeneously. The monofilaments may be round or rectangular. Examples of rectangular nylon monofilaments and twisted stem tools made therefrom are seen in the above noted Schieder et al. U.S. Pat. No. 5,329,730. Examples of tapes are shown in Tyler et al. U.S. Pat. Nos. 5,129,197 and 5,155,945.
Usually, the more filaments or tapes in the bundle which can be secured by the stem, the more effective and aggressive the tool. However, this also creates problems in making twisted stem tools.
With a large bundle, the stem has to be twisted tight. The material, however, has a compressive strength of only about 8000 psi (563.64 Kg/cm.sup.2). Some fill materials such as certain types of wire have compressive strengths of 280,000 psi (19727.3 kg/cm.sup.2). However, to get the proper twist, the wire at the bundle has to be gripped tightly to resist the torque of the twist. If the wire is crescent-shaped or even round, stress concentrations may easily result which can damage or fracture the fill material. For this reason, the shape of the wire or cotter pin is important as it bears against the fill material. Points of stress concentration need to be avoided. Accordingly, the chuck gripping the wire or pin at the bight needs a firm grip but at reduced pressure. In this manner, the clamping force during manufacture should not exceed the compressive strength of the fill material.
All of the above creates a further problem, particularly for larger tools, such as tools having stems 0.250 inches (6-7 mm) or more. The problems are accentuated when a large amount of fill material is employed to provide a tough and aggressive abrading action. The bundle when tightly formed tends to separate the legs of the stem and if the tool is rotated in a reverse direction repeatedly the stem may tend to unwind. The stems are typically held in the chuck of a power tool and a common chuck would be a three or six jaw Jacob's style chuck. On half-round cotter pin wire which is twisted, such chucks may give less than adequate purchase, particularly if the tool is repeatedly cycled in reverse which is often the case.
Accordingly, there is a need for a twisted stem tool capable of taking advantage of the fill material of the type mentioned in substantial amounts, and which will perform in aggressive applications, with a long useful life. There is also a need for a method of making such tool.